The U.S. Navy says one person is injured after a shooting at a Navy building in Washington. Police and emergency crews gathered Monday morning outside the Naval Sea Systems Command Headquarters building, where the shooting was reported. (AP Photo/Jacquely

WASHINGTON — The D.C. mayor says 13 people have died in the shooting rampage, including the gunman.

Mayor Vincent Gray said at a news conference Monday afternoon that the shooter was among the dead. Officials say the gunman has been identified as 34-year-old Aaron Alexis.

Earlier in the day, authorities had been looking for two other people who may have been involved in the shooting. One of those people has been identified and ruled out as a suspect.

However, Gray says investigators are still searching for a third individual wearing an olive-green, military-style uniform to determine if he was involved.

Gray says a motive has not yet been determined.

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WASHINGTON — Police say at least 12 people have died in the shootings at the Washington Navy Yard.

D.C. Police Chief Cathy Lanier said during a news conference Monday that 12 people were confirmed dead.

Lanier says people are being told to stay in their homes and out of the area as authorities search for two other possible suspects. One of the shooters has died.

The police chief says officers are searching for two other people with firearms wearing military-style uniforms.

She says there is no indication of a possible motive at this time.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

As many as three gunmen opened fire Monday inside one of the Navy's oldest buildings, attacking office workers at a heavily guarded military facility in the heart of the nation's capital. At least six people were killed.

One of the gunmen was dead, and police were searching for two other men believed to have joined in the attack at the Washington Navy Yard. The suspects were reportedly dressed in military-style clothing, including one who had on a beret.

In all, more than a dozen people were shot, at least half of them fatally. It was not immediately clear whether that number included the dead gunman.

The attack unfolded just a short distance from the White House and the U.S. Capitol at a former shipyard that is one of the Navy's oldest shore facilities.

The building that was targeted was the military's headquarters for Naval Sea Systems Command, which buys, builds and maintains ships, submarines and combat systems. About 3,000 people work at the headquarters, many of them civilians.

Witnesses described a gunman opening fire from a fourth-floor overlook, aiming down on people in the first-floor cafeteria. Others said a gunman fired at them in a third-floor hallway.

It was not clear whether the witnesses on different floors were describing the same gunman.

As emergency vehicles and law enforcement officers flooded streets around the complex, a helicopter hovered overhead, nearby schools were locked down and airplanes at nearby Reagan National Airport were briefly grounded so they would not interfere with law-enforcement choppers. Less than 2 miles away, security was beefed up at the Capitol and other federal buildings, but officials said there was no known threat.

President Barack Obama mourned yet another mass shooting in the U.S. that he said took the lives of American patriots. Obama promised to make sure "whoever carried out this cowardly act is held responsible."

Two Navy officials confirmed at least six people had died. The officials spoke on condition of anonymity because they were not authorized to talk about the situation publicly.

Todd Brundidge, an executive assistant with Navy Sea Systems Command, said he and other co-workers encountered a gunman in a long hallway on the third floor. The gunman was wearing all blue, he said.

"He just turned and started firing," Brundidge said.

Terrie Durham, an executive assistant with the same agency, said she also saw the gunman firing toward her and Brundidge.

"He aimed high and missed," she said. "He said nothing. As soon as I realized he was shooting, we just said, 'Get out of the building.'"

Rick Mason, a civilian program-management analyst for the Navy, said a gunman was shooting from the overlook in the hallway outside his office.

Shortly after the gunfire, Mason said, someone on an overhead speaker told workers to seek shelter and later to head for the gates at the complex.

Patricia Ward, a logistics-management specialist, said she was in the cafeteria getting breakfast.

"It was three gunshots straight in a row — pop, pop, pop. Three seconds later, it was pop, pop, pop, pop, pop, so it was like about a total of seven gunshots, and we just started running," Ward told reporters several blocks away from the Navy Yard.

Ward said security officers started directing people out of the building with guns drawn.

One person died at George Washington University Hospital of a single gunshot wound to the left temple, said Dr. Babak Sarani, director of trauma and acute care surgery. A police officer and two civilian women were in critical condition at Washington Hospital Center, said Janis Orlowski, the hospital's chief operating officer.

Orlowski said the police officer was in the operating room with gunshot wounds to the legs. One woman had a gunshot wound to the shoulder. The other had gunshot wounds to the head and hand.

Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget. Only security personnel were allowed to be armed on the campus.

The Navy Yard has three gates, according to its website. One is open around the clock and must be used by visitors. A second gate is only for military and civilian Defense Department employees. The other gate is for bus traffic.

The Navy Yard is part of a fast-growing neighborhood on the banks of the Anacostia River in southeast Washington, just blocks from the Nationals Park baseball stadium.

Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

WASHINGTON — At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and officials said six people were killed and at least four were wounded, including a law enforcement officer.

Police were looking for two other potential gunmen wearing military-style uniforms, including one who had on a beret, chief Cathy Lanier said. One had a long gun and the other was also armed, she said. One of the three gunmen had died, though Lanier didn't say how.

Witnesses described a gunman opening fire from the fourth floor, aiming down on people in the first-floor cafeteria. Others said a gunman fired at them in a third-floor hallway. It wasn't clear whether the witnesses on different floors were describing the same gunman.

As witnesses emerged from the building, a helicopter hovered over it, schools were on lockdown and airplanes at nearby Reagan National Airport were briefly grounded so they wouldn't interfere with law enforcement helicopters. Less than 2 miles away, security was beefed up at the Capitol, but officials said there was no known threat there. President Barack Obama was getting frequent briefings on the shooting.

Two Navy officials confirmed at least six people had died. The officials spoke on condition of anonymity because they were not authorized to discuss the situation publicly.

About 3,000 people work at the Naval Sea Systems Command headquarters, which builds, buys and maintains the Navy's ships and submarines and combat systems.

Todd Brundidge, an executive assistant with Navy Sea Systems Command, said he and other co-workers encountered a gunman in a long hallway of their building on the third floor. The gunman was wearing all blue, he said.

"He just turned and started firing," Brundidge said.

Terrie Durham, an executive assistant with the same agency, said she also saw the gunman firing toward her and Brundidge.

"He aimed high and missed," she said. "He said nothing. As soon as I realized he was shooting, we just said, 'Get out of the building.'"

Rick Mason, a program management analyst who is a civilian with the U.S. Navy, said a gunman was shooting from a fourth floor overlook in the hallway outside his office. He said the gunman was aiming down at people in the building's cafeteria. Mason said he could hear the shots but could not see a gunman.

Shortly after the gunfire, Mason said someone on an overhead speaker told workers to seek shelter and later to head for the gates at the complex.

Patricia Ward, a logistics management specialist, said she was in the cafeteria.

"It was three gunshots straight in a row — pop, pop, pop. Three seconds later, it was pop, pop, pop, pop, pop, so it was like about a total of seven gunshots, and we just started running," Ward told reporters several blocks away from the Navy Yard.

Ward said security officers started directing people out of the building with guns drawn.

Police and federal agents from multiple law enforcement agencies responded. Ambulances were parked outside, streets in the area were closed and departures from Reagan National Airport were temporarily halted for security reasons.

Janis Orlowski, chief operating officer of Washington Hospital Center, told reporters the hospital was treating three gunshot victims in critical condition. One was Washington, D.C., metropolitan police officer and two were civilian women.

A U.S. Park Police helicopter hovered over the building and appeared to drop a basket with a person onto the roof.

District of Columbia schools officials said 12 public and charter schools and one administrative building in the vicinity of the Navy Yard were placed on lockdown. The action was taken out an abundance of caution, schools spokeswoman Melissa Salmanowitz said.

Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget. Only security personnel were allowed to be armed on the campus.

The Navy Yard has three gates, according to its website. One is open 24 hours a day, seven days a week, and must be used by any visitors. A second gate is only for military and civilian Defense Department employees and the other is for bus traffic.

The Navy Yard is part of a fast-growing neighborhood on the banks of the Anacostia River in southeast Washington, just blocks from Nationals Park.

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WASHINGTON — Authorities say they are looking for two additional suspects in the shooting rampage at the Washington Navy Yard.

Lanier says one police officer was wounded in an exchange of gunfire with a shooter. She says one shooter has been killed.

Two Navy officials say at least six people were killed in the rampage.

D.C. Mayor Vincent Gray said at a Monday news conference four people were wounded and taken to hospitals.

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WASHINGTON — Two officials say police are looking into the possibility of a second shooter at the Washington Navy Yard where several people were killed.

A Defense Department official and a law enforcement official spoke on condition of anonymity Monday because they were not authorized to discuss the ongoing investigation.

At least one gunman opened fire inside the Naval Sea Systems Command headquarters, where about 3,000 people work just miles from the Capitol.

Among the wounded was a D.C. police officer, according to a law enforcement official who spoke on the condition of anonymity because the person was not authorized to discuss an ongoing investigation.

At least 10 were wounded.

Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Below is an earlier report:

A gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and a Defense Department official said several people were killed and as many as 10 were wounded, including at least one law enforcement officer.

A shooter was "contained" but not yet in custody, according to the official, who spoke on condition of anonymity because they were not authorized to discuss the matter publicly. Helicopters swarmed overhead, schools were on lockdown and airplanes at nearby Reagan National Airport were grounded as authorities swarmed the area in southeast D.C., just miles from the Capitol.

About 3,000 people work at the Naval Sea Systems Command headquarters.

The exact number of people killed and the conditions of those wounded was not immediately known.

Rick Mason, a program management analyst who is a civilian with the U.S. Navy, said a gunman was shooting from a fourth floor overlook in the hallway outside his office. He said the gunman was aiming down at people in the building's cafeteria on the first floor. Mason said he could hear the shots but could not see a gunman.

Shortly after the gunfire, Mason said overhead speakers told workers to seek shelter and later to head for the gates at the complex.

Patricia Ward, a logistics management specialist, said she was in the cafeteria and heard shots. They sounded like "pop, pop, pop," she said. After a few seconds, there were more shots, she said.

"Everybody just panicked at first," she said. "It was just people running, running, running."

Ward said security officers started directing people out of the building with guns drawn.

Police and federal agents from multiple law enforcement agencies responded to the scene. Ambulances were parked outside, streets in the area were closed and departures from Reagan National Airport were temporarily halted for security reasons.

Among the wounded was a D.C. police officer, according to a law enforcement official who spoke on the condition of anonymity because the person was not authorized to discuss an ongoing investigation.

A U.S. Park Police helicopter hovered over the building and appeared to drop a basket or a stretcher with a person onto the roof.

Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget. It builds, buys and maintains the Navy's ships and submarines and their combat systems.

Keep visiting JohnsonCityPress.com for updates on this developing story.

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WASHINGTON —Several people were injured in a shooting Monday morning at a building at the Washington Navy Yard, the U.S. Navy said, and authorities searched for an active shooter.

A defense official, who spoke to The Associated Press on condition of anonymity because he was not authorized to speak during an active attack, also said there were at least several injuries.

The Navy said shots were fired around 8:20 a.m. at the Naval Sea Systems Command headquarters, where about 3,000 people work.

The number of the victims and their conditions was not immediately known, though the Navy said multiple people had been injured.

Police and federal agents from multiple law enforcement agencies responded to the scene. Ambulances were parked outside, streets in the area were closed and flights at Reagan National Airport were temporarily halted.

A U.S. Park Police helicopter hovered over the building and appeared to drop a basket or a stretcher with a person onto the roof.

Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget. It builds, buys and maintains the Navy's ships and submarines and their combat systems.